1. Field of the Invention
The invention relates to an overlap mark set and a method for selecting a recipe of measuring overlap error.
2. Description of Related Art
The photolithography process plays a very important role in manufacturing semiconductor devices. Its accuracy in transferring the pattern has a great influence on the yield rate of the products. Therefore, the process must be monitored constantly, so as to ensure the pattern on the photomask is correctly transferred onto the wafer. The photolithography process is usually monitored by forming an overlap mark on a wafer, so as to check the alignment accuracy between the pre-layer and the post-layer. The most common overlap mark is the box-in-box (BIB) overlap mark. As the line width in the manufacturing process of integrated circuits continuously decreases, the alignment accuracy between the upper and lower wafer layers becomes more and more important. If the recipe (e.g. light source, aperture, filter, etc.) used is inappropriate, the actual overlap error may not be precisely measured.